The present invention is directed to a control process for a roll stand for rolling a strip, and in particular to a four-high or a six-high stand having at least one pair of work rolls and one pair of backup rolls, both mounted on roll bearings. As an option, the stand may include one pair of intermediary rolls, also mounted on roll bearings. The present invention is directed to a control process for roll stands of the type having controls for a rolling force, for a deflecting force, and, as an option, for a roll shift. The roll stand also includes a roll stand model with a deflection model, in which the roll stand model is assigned a specified roll gap variation, and the roll stand model calculates from the specified roll gap variation a plurality of on line set points for the rolling force, for the deflecting force, and, optionally, for the roll shift.
Control processes for roll stands in general are in wide use. The differential equations for calculating the deflection and the variation of forces during a rolling operation, as well as the solutions of these differential equations, are well known in principle. The solution algorithms used, however, converge very slowly. Therefore, they cannot be used on-line. For this reason, tables have been calculated for obtaining, through interpolation, the relationship between on the one hand the rolling force and the deflecting force and, optionally, the roll shift, and on the other hand the roll gap variation. Use of such tables, however, has proven extremely rigid and inflexible, particularly when individual rolls of the roll stand are replaced, because in that situation the tables must be completely recalculated.